Device for Freezing,Transporting and Thawing Fluids

ABSTRACT

The invention relates to a device ( 1 ) for freezing, transporting and thawing fluids, in particular sterile liquids, solutions and suspensions for the chemical, biotechnology, pharmaceutical and food industries. Said device comprises a container ( 10 ) with a lid ( 20 ), a wall ( 40 ) and a base ( 30 ) and at least one heat exchanger element ( 50 ) that is operatively connected to the fluids held in the container, such that said fluids can be cooled or heated. An immersion pipe ( 60 ) is operatively connected to at least one heat exchanger element ( 50 ) via at least one sub-region of its longitudinal extension, said region preferably extending approximately from a lowest point in the container to a maximum fill level. Preferably, the immersion pipe is in direct contact with at least one heat exchanger element and can be passively heated. During the thawing process, the thus liquefied product is withdrawn via the heatable immersion pipe(s), which preferably penetrate(s) the interior of the container from top to bottom and open(s) over the lowest point in the container. In comparison to known devices, in which the feed pipe is freely located in the container interior and thus freely located in the frozen product, the advantage of the heatable immersion pipe is that the frozen product thaws extremely quickly inside the immersion pipe and the withdrawal of the thawed liquid product is only blocked in the initial phase of the thawing process. During withdrawal, the thawed product is, in addition, gently heated during its passage through the heated immersion pipe, such that it can be fed, preferably from above, onto portions of the product that are still frozen at a temperature that is significantly higher than the freezing point, thus accelerating the thawing process.

FIELD OF THE INVENTION

This invention relates to a device for freezing, transporting andthawing fluids, in particular sterile fluids, solutions and suspensionsfor the chemical, biotechnological, pharmaceutical and food industry, ofthe type defined in claim 1 and a method of thawing such fluids asdefined in claim 10.

BACKGROUND OF THE INVENTION

Increasing globalisation of production processes used for production inthe chemical, pharmaceutical and biotechnological industry but also inthe food industry have placed more and more demands on the logisticsinvolved in storing and transporting product stages, e.g. from cellcultures, for downstream processing. In order to deal with this problem,it has become increasingly necessary to freeze smaller or larger batchesof liquid intermediate and/or end products and transport the frozenbatches. Various devices suitable for this purpose are known from theprior art, which comprise a container with a freeze-thaw unit, by meansof which batches of a few to several hundred litres can be frozen.

For example, patent specification U.S. Pat. No. 5,524,706 discloses adevice with an upright cylindrical container with a funnel-shaped basewith a central outlet orifice. The container wall and base are of adouble-skin design and coolant flows through them during the freezingprocess. In order to ensure gentle and uniform freezing, a plurality ofcooling elements is provided in the container. The cooling elements arehollow cylinders, the diameters and lengths of which are adapted to oneanother so that they are disposed concentrically with one another andextend through the container interior respectively from a top region,which predefines the maximum filling level, to approximately the base.The distance of the cooling elements from the container base and of thecooling elements from one another is the same overall. Coolant can befed in and out of top-end pipes connecting all the cooling elements viaa single inlet pipe and outlet pipe on the top face of the lid. Forthawing purposes, an appropriately warm medium is fed through thecooling elements and once the container contents have completely thawed,the container is emptied via the central bottom outlet orifice in theregion of the deepest point of the container. Since the cooling elementsdisclosed in U.S. Pat. No. 5,524,706 occupy a large part of thecontainer volume and have a very large surface area, freezing andthawing is quick and gentle and does not require additional processsteps. For economic reasons, however, it is very desirable to reduce thesize of the cooling elements massively in order to save on costs andincrease the usable volume of the container.

The applicant has developed a freezing and transport device for whichthe freezing process was quantified in terms of temperatures and phasetransitions on the basis of time and location. The device, known underthe brand name FreezeContainer®, is illustrated in FIGS. 1 a and 1 band, with a scalable volume of up to 300 litres, offers a whole seriesof advantages. The weight of the device is more than 10% less than isthe case with other known devices. FreezeContainer® has an optimalsterile design with very good CIP properties. The design of the coolingelements ensures a phase transition that is homogenous in timethroughout the kettle volume, which in turn guarantees short processtimes. Apart from these advantages, the general design of the device issufficiently variable to enable the FreezeContainer® to be integrated incomplex production procedures and thus fulfil the high demands placed onit by the pharmaceutical industry in terms of functional and processreliability.

For thawing purposes, a warm medium is fed through the container wall,container base and the cooling coil. The thawing process is preferablyassisted by shaking the container lightly.

The closed container is filled with fluids, in particular sterilefluids, solutions and suspensions for the chemical, biotechnological,pharmaceutical and food industry, hereafter referred to as product, fromthe top via an inlet pipe mounted in the cover. The inlet pipe opensexactly above a central outlet orifice at the deepest point of the baseso that the product can be drawn off through the base outlet or via theinlet pipe once it has completely thawed.

In order to increase the already high degree of functional versatilityand process adaptability still further, it is desirable to be able topump the product in circulation during thawing, which is not possiblewith the existing device.

SUMMARY OF THE INVENTION

Accordingly, the objective of this invention is to propose a device forfreezing, transporting and thawing fluids, in particular sterile fluids,solutions and suspensions for the chemical, biotechnological,pharmaceutical and food industry, which does not have the disadvantagesof the known devices and which permits a maximum amount of operatingoptions. Another objective of the invention is to propose a device and amethod whereby the frozen product can be thawed more rapidly and gentlythan in the past whilst simultaneously facilitating mixing of the thawedsubstrate.

These objectives are achieved by a device as defined in claim 1 and amethod as defined in claim 10, by means of a heated immersion pipe whichthaws at an early stage and therefore enables thawed and preferablypre-heated product to be pumped in circulation, i.e. drawn off andrecirculated, during the entire thawing process. The disadvantages ofthe known methods are avoided and more rapid thawing is achieved.

The new device proposed by the invention has at least one immersion pipewhich has an active thermal connection to the heat exchanger elements atleast across a part-region of its longitudinal extension, whichpreferably extends from approximately a deepest point of the containeras far as a maximum filling level. The maximum filling level is thefilling level to which the container can be filled with product to befrozen and then thawed on a controlled basis. It is primarily defined bythe position of the heat exchanger elements, making allowance for theexpansion in volume caused by changes in density. In the case of theembodiments described below, it is between a top container edge and topportions of the heat exchanger elements. The immersion pipe ispreferably in direct contact with at least one heat exchanger elementand can be passively heated. During thawing, liquefied product can bedrawn off from at least one heatable immersion pipe, which in turnpreferably extends through the container interior from above and opensabove a deepest point of the base. The heatable immersion pipe has anadvantage over the known devices, in which the inlet pipe is disposedfreely in the container interior and hence freely in the frozen product,because the frozen product thaws very rapidly in the interior of theimmersion pipe and the process of drawing off the thawed liquid productis blocked only during an initial phase of the thawing process. Whilstit is being drawn off, the thawed product is also gently heated as itpasses through the heated immersion pipe so that it can be discharged ata temperature significantly above freezing point, preferably from above,onto parts of the product still frozen and accelerates the thawingprocess. In a preferred embodiment of the invention, return pipes areprovided on the internal face of the container lid for this purpose.

Heating the thawed product in the immersion pipe as it is drawn offoffers a significant advantage over drawing it off from an outletorifice in the base. In the case of a device of the type known from U.S.Pat. No. 5,524,706, the thawed product is drawn off through the bottomoutlet and the product is at a temperature that is only just abovefreezing point. When this cold product is pumped through the filler neckonto the still frozen product, this barely accelerates the thawingprocess. In the case of the invention, the product pumped onto the stillfrozen parts is now pre-heated, which significantly speeds up thethawing process. Furthermore, drawing off the thawed product through theoutlet orifice in the base is technically a disadvantage in terms ofconductance.

Another advantage of the new device resides in the fact that thedistance which the liquid product must travel as it is being pumped outof the container can be kept very short because it does not have to bedirected from the outlet in the base to the inlet in the lid of thecontainer. This obviates the need for undesirable pipes on the outsideof the container on the one hand and discharging and emptying as well aspumping conveniently take place from the top of the new device on theother hand, because all connectors can be disposed in the lid or atleast in a top region of the container.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the stirrer proposed by the invention will bedescribed below with reference to the appended drawings. Of these:

FIG. 1 a shows a longitudinal section through a freeze-thaw containerbased on the prior art with a cooling element in the interior of thecontainer and a base outlet;

FIG. 1 b is a side view of the container illustrated in FIG. 1 a, inwhich an inlet pipe may be seen, the fittings disposed in the interiorbeing shown by broken lines;

FIG. 2 a is a longitudinal section through a container of a device basedon an embodiment of the invention, in which a cooling element and animmersion pipe are illustrated although not in section;

FIG. 2 b is a view from above at an angle showing an immersion pipebased on one embodiment, actively co-operating with a cooling coil,where only the parts which lie in the interior of a container areillustrated;

FIG. 3 is a longitudinal section through a device based on anotherembodiment of the invention with an immersion pipe extending on thewalls, and again a cooling element is illustrated but not in section;

FIG. 4 is a side view of a device based on another embodiment of theinvention, in which the internally lying fittings are illustrated bybroken lines;

FIG. 5 a is a view from below at an angle showing a lid of a deviceillustrated in FIG. 2 with cooling, immersion and return elementsmounted on the lid; and

FIG. 5 b is a side view of the lid and cooling, immersion and returnelements illustrated in FIG. 5 a.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 a is a longitudinal section illustrating a freeze-thaw containerB designed by the applicant. As explained above, this container is knownfrom the prior art under the name of FreezeContainer. The container Bcan be closed and sealed by means of a top lid BD. Together with abottom base BB and a side wall BS, the lid BD defines an interior I ofthe container B, in which a cooling coil KS is disposed. As indicated inFIG. 1 a, the cooling coil is connected so as to communicate with thedouble-skin inner container wall by means of an isolated cooling pipeKL. Coolant fed in through an appropriate inlet pipe AM to thedouble-skin container wall BW, flows through the container wall BW andbase BB via the cooling pipe KL and is then directed through the coolingcoil KS. It will be clear to the person skilled in the art thattechnically reversible processes of freezing and thawing can be effectedusing the device illustrated in FIG. 1 and with other similar genericdevices on which the invention is based. For the sake of simplicity,therefore, the essential elements of the devices will primarily bedescribed in the context of cooling. Where cooling elements, coolingcoils and similar elements are mentioned below, it is clear that theseheat exchanger elements are suitable not only for circulating a coldmedium or a medium used during a freezing process, but also forcirculating and co-operating with a warm medium during the thawingprocess.

The geometry of the cooling coil KS is designed to produce an optimumsequence of temperatures and phase transitions in time and locally inthe container interior I and is connected to a plurality of verticallyextending portions E_(V), which are each mutually connected via top,respective bottom horizontal portions E_(H). Whilst the top and bottomhorizontal portions E_(H) respectively lie more or less in one plane, avertical portion E_(Z) disposed centrally in the container extendsfarther down into the container to just short of a deepest point. Thisensures that the region directly above a central outlet orifice A in thecontainer base BB is thawed early during the thawing process. This hasproved to be of particular advantage because it is very difficult toprovide heat exchanger elements in the region of the base outlet. Thetop horizontal part-pieces EHO facing the lid BD extend in a region justbelow the maximum filling level FH of the container B, respectivelydefine the maximum filling level. The vertical part-pieces at thebeginning and at the end of the cooling coil extend through thecontainer lid BD and are respectively connected to a coolant inlet ZMand to the cooling pipe KL and thus indirectly to the outlet AM.

The freeze-thaw container B illustrated in FIG. 1 with a usable capacityof 300 litres is of an essentially cylindrical shape with a centrallongitudinal axis L. Freeze-thaw containers B of the generic typeusually have a capacity of a few to several hundred litres.

FIG. 1 b is a side view of the freeze-thaw container B illustrated inFIG. 1 a, rotated by 90°, in which an inlet pipe ZR may be seen,connected so as to establish a communication from the lid top face tomore or less the deepest point in the interior I of the container B.Extending through the inlet pipe ZR between two vertical portions E_(V)and more or less at an equal distance from them is a top verticalpipe-piece ZV. Above a bottom horizontal portion E_(HU), it bends downand is directed by means of a portion ZS lying at an angle as far as thedeepest point T of the container B, where it opens through an orificeZO.

The container B is preferably filled with the product to be frozenthrough the inlet pipe ZR in the closed state, i.e. with the lid fitted.Once the desired filling level is reached, an appropriate inlet valve atthe upper end of the inlet pipe is closed and the cooling processinitiated by circulating cold medium through the cooling circuit which,in addition to the cooling coil and the container wall and containerbase, additionally comprises at least one pump, not illustrated in thedrawing, and a cooling unit or coolant reservoir, also not illustratedin the drawing, until the product in the container interior has beencompletely frozen on a controlled basis and the minimum temperaturedesired for storage or transport has been reached. In this state, theproduct, which is also disposed in the interior of the inlet pipe ZR, isfrozen and the latter blocked. For thawing purposes, a warm medium iscirculated through the circuit and in order to accelerate the thawingprocess, the container, which is mounted on a base stand P, is lightlyshaken. The deeply extending, central vertical piece EZ ensures that theregion above the central outlet orifice is thawed relatively quickly.Although the inlet pipe ZR opens exactly into this region, the thawedproduct can not be drawn down until the entire volume of the inlet pipehas thawed. As briefly explained above, this is not achieved untilpractically all the product has thawed. Thawed product can be drawn offrelatively early during the thawing process through the bottom centraloutlet orifice A, which communicates via an outlet pipe AL with anoutlet connector AA in an end face of the base stand P. However, sincethe known container does not have any means of recirculating thisliquefied product, it can not be pumped back round. Furthermore, theproduct contained above the bottom central outlet orifice A is stillvery cold and would barely have the effect of assisting the thawingprocess if it were recirculated through the container interior.

FIG. 2 illustrates a preferred embodiment of the freeze-thaw device 1proposed by the invention, which is based on the freeze-thaw container Bdescribed above. As illustrated in the longitudinal section shown inFIG. 2 a, a new feature in the form of an immersion pipe 60 is providedin the freeze-thaw container 10. At a first end above a lid 20, theimmersion pipe is preferably provided with a fitting 64 comprising aninlet connector 65 and an outlet connector 66 and co-operating valves67, 68 and a shut-off valve 69. From the fitting 64, the immersion pipe60 extends downwards by means of a first vertical portion, runs throughthe lid 20 and is then run above a lid bottom edge 21 with a slightgradient via a radial part-piece 52 to the centre of the more or lesscylindrical container interior 11. On reaching the containerlongitudinal axis L, the immersion pipe 60 then bends downwards andextends by means of a second central vertical piece 63 along the centralaxis L to more or less the deepest point of the container interior,where it opens through an orifice 63′. More or less along the entirecourse of the longitudinal axis L, the immersion pipe 60 isconcentrically surrounded by a coaxially extending vertical part-piece51 of a cooling element. In terms of design, the other portions of thecooling element conform to the essentially tried and tested shape usedfor the applicant's known FreezeContainers described above. The wall 30and base 40 of the container 10 are also based on the known double-skindesign and contribute to the heat exchange process. The advantageachieved by the invention as a result of the new technical feature isthat the portion of the immersion pipe 60 disposed between the containerbase 30 and the maximum filling level F_(MAX) establishes an optimumactive communication with the heat exchanger element extending freelythrough the container interior, namely the cooling coil 50.

During pumping, the disposition of the immersion pipe and cooling coiland/or other heating elements ensures that the lumen of the immersionpipe thaws very quickly after the start of circulating warm mediumthrough the circuit. The thawed product, which in turn collects at thedeepest point of the container, can be drawn off upwards through theimmersion pipe 60 at an early point during the thawing process. Thesecond, extremely advantageous effect is that the still very coldliquefied product is heated as it is conveyed through the centralpart-piece 63 because warm medium is flowing round its entirecircumference.

The central part-piece 63 of the immersion pipe preferably forms theinner wall of the hollow cylindrical part-piece 51 of the cooling coilso that the immersion pipe and cooling coil are integrally connected toone another in a “pipe in pipe” arrangement and the immersion pipe isintegrated in the region of the cooling element that is directlythermally active. A lowermost part-piece 63′ of the immersion pipe is nolonger surrounded by the vertical part-piece 51 of the cooling coil andextends down out of it by a few centimetres. The lowermost part-piece63′ can be very easily adapted to the size of the container 10 bycutting it to a length that will ensure that the bottom opening of theimmersion pipe still lies at the desired short distance of preferably 5mm but at least 1 mm from the container base or lies in the base via abottom outlet orifice, including in the warm state (e.g. during thawingand pumping). For example, existing devices can be retro-fitted with thecombination of cooling element and immersion pipe proposed by theinvention, as illustrated in FIG. 2 b with the portions lying underneaththe lid, and the length of the immersion pipe can be readily and exactlyadapted on site. The loss of product which can not be drawn out of thecontainer can be easily minimised as a result. In the advantageousembodiment of the invention illustrated in FIG. 2 b, the immersion pipehas an internal diameter of 18.1 mm and a wall thickness of 1.6 mm. Thecentral part-piece 51 of the cooling coil has a diameter of 42.4 mm inthe case of a container with a usable volume of 300 litres for example,and the remaining portions of the cooling coil have a diameter of 21.3mm respectively. The free flow cross-section in the cooling coil istherefore kept approximately the same in all part-pieces as a result.The individual part-portions of the immersion pipe and cooling coil arepreferably made from austenitic steel, for example 4435/316L, andHastelloy, and welded to one another orbitally and manually using aTungsten Inert Gas (TIG) process. In order to make manufacture of the“pipe in pipe” solution as efficient as possible and to ensure that itcan be cleaned without any difficulty, it has proved to be of advantageif a top inlet point of the central part-piece 63 of the immersion pipe60 into the central vertical piece 51 of the cooling coil 50 and anappropriate bottom outlet orifice are closed by means of an annularstopper 53. The heat exchange medium is fed to and/or away from thecentral, vertical part-piece 51 of the cooling coil 50 via a tophorizontal part-piece 56 and a bottom inclined part-piece 57,respectively disposed in the immediate vicinity of the respective endsof the vertical part-piece 51 and open laterally into it.

The immersion pipe and cooling coil may also be manufactured in twopieces and inserted one in the other so that the immersion pipe wallcomes into contact with an internal wall of the central part-piece 51.The one-piece design may be used for containers that will be used morethan once because it is significantly easier to clean.

The thawing process and the drawing-off of thawed product will bedescribed below with reference to FIG. 2 a. It is assumed that thefreeze-thaw container 10 is filled with frozen product to a maximumfilling level F_(MAX). When warm medium is now directed through thecooling coil, the substrate S in the active region WB of the heatexchanger elements, i.e. in the active region of the cooling coil andthe double-skin container wall and double-skin container base, isthawed, preferably gently and slowly.

As indicated in FIG. 2 a, the parts of the cooling coil disposed lowdown, namely the bottom inclined radial piece 57 of the cooling coil andthe bottom region of the central part-piece 51, ensure that the producton and around the deepest point of the container thaw very quicklyduring the thawing process. Within the meaning of the invention, thelumen of the central portion 63 of the immersion pipe 60 is one of thefirst regions in the container interior to become free of ice. Thethawed product, which collects at the deepest point of the container 10,can therefore be drawn off from the container 10 at a very early stageof the thawing process. As it is conveyed further upwards through thecentral immersion pipe portion, the liquefied product is heated and,when valves 69 and 68 are open, fed via the outlet connector 66 of thefitting 64 to a fluid conveyor unit not illustrated in the drawings,preferably a conveyor or a pump. The pre-heated product is conveyed bythe latter through a return line 70, as illustrated in FIG. 5 with itsparts on the lid top face and on the lid bottom face, back into theinterior of the container 10. In the side view onto said lid/cover 20illustrated in FIG. 5 b, the conveyor means (for example a pump) and thepipes connecting the outlet connector 66 of the immersion pipe fitting64 and an inlet connector 71 above the lid to one another are notillustrated. When valve 72 is open, the heated product is fed back intothe container via the return line 70, which extends through the lid 20by means of a vertical piece 73 and a downwardly angled leg 74. Aterminal outlet orifice 75 of the tubular leg 74 opens laterally onto avertical part-piece of the cooling coil above the level defined by themaximum filling level F_(MAX). As it is pumped round, the pre-heatedproduct is directed onto the frozen product surface from above and thusassists the thawing process from above. The position of the outletorifice 75 of the tubular leg 74 is such that the circulated product isdirected onto the vertical part-piece of the cooling coil. Thissignificantly reduces the formation of foam as the product is beingpumped round.

The combination of removing and pre-heating thawed product with animmersion element 60 proposed by the invention and recirculating it viathe direct return line 70 at an early point in time at which a majorpart of the product in the interior 11 of the container 10 is stillfrozen leads to rapid and gentle thawing.

Instead of running the immersion pipe through the central part-piece ofthe cooling coil as described above, it is run in an alternativearrangement, as illustrated in FIG. 4, in another advantageousembodiment of the invention. In this instance, the immersion pipe 60′extends through a part-piece 51′ of a cooling coil 50′ running parallelin an upper region between the container wall 40 and longitudinal axis Land inclined towards the deepest point of the container 10 in a bottomregion. This construction again ensures that the immersion pipe isconcentrically surrounded by the expediently adapted part-piece 51′ ofthe cooling coil 50′ along the entire distance from the deepest point ofthe container to the maximum filling level.

In other embodiments, the immersion pipe surrounds the cooling coil sothat the immersion pipe lies on the outside in the “pipe in pipe”construction and is cooled or heated by the internally lying part-pieceof the cooling coil. These embodiments are less preferred in terms ofheat conduction. The same applies to embodiments in which the immersionpipe and a co-operating part-piece of the cooling coil are designed asmutually abutting half-pipes, since this also results in poorer flowdynamics.

FIG. 3 illustrates another embodiment in which an immersion pipe 80 isactively connected to a double-skin container wall 40′ and a double-skincontainer base 30′ rather than to a cooling coil KS. To avoid making itmore difficult to clean the container interior, the immersion pipe 80 iscompletely recessed into the wall 40′ and base 30′ and opens by means ofa bottom orifice 81 in the region of the deepest point of the container10′, preferably in a central, bottom outlet orifice 31′ in the base 30′.In the top region of the container wall 40′, the immersion pipe runs tothe outside and establishes a connection communicating with thecontainer interior via a lateral connector 82. In order to avoidadversely affecting the flow of heat exchange medium in the containerwall and base, the immersion pipe may also be run along the externalfaces of the double-skin container wall 40′ and double-skin containerbase 30′, in other words essentially in the insulation casing 12.

The inventive idea of placing an immersion pipe in active communicationwith heat exchanger elements is not restricted to the elementsspecifically described and illustrated in the drawings so far andinstead, can be used with a plurality of other elements. Freeze-thawelements with heat exchangers disposed in a spiral shape may be placedin active communication with an immersion pipe for drawing off andpre-heating product, as well as plate-shaped or star-shaped heatexchanger elements.

The decisive factor is that a thermal connection exists between the heatexchanger element and at least the portion of the immersion pipe whichlies in the region of the frozen product, namely approximately from thedeepest point of the container as far as the maximum filling level,respectively where it is filled with it in the frozen state. A directcontact between the immersion element and the heat exchanger elementbased on the “pipe in pipe” design and the “pipe in wall” designdescribed above is not absolutely necessary but is of advantage.

The technical teaching of the invention may also be used for disposabledevices, which are becoming increasingly popular as they areparticularly economic in the CIP/SIP sector due to reduced costs. In thecase of such “single-use” devices, the entire device may be made fromappropriate plastics in a genuine disposable version. In anotherembodiment, the thermally passive parts, in other words essentially thebase, lid and wall of the container and the immersion pipe, may be madefrom plastic as “disposables”, whilst the heat exchanger elements aremade from metal and are removed from the container after use, cleanedand re-used.

FIG. 5 illustrates a spray pipe 90, which is used for cleaning/CIP thecontainer interior with its fittings. Cleaning solution is fed in via aconnector 91 which, in the embodiment illustrated as an example, issprayed by spray heads fitted to the ends of two spray pipes. The factthat the cooling coil and immersion pipe are free of fins, componentsand baffle plates with a large surface area means not only that thesurfaces to be cleaned, but also the spray blind spots are reduced to aminimum. This also contributes to the fact that cleaning and CIP/SIP ofthe device proposed by the invention is extremely simple and efficient.

In another embodiment, the immersion pipe, which essentially correspondsto that illustrated in FIG. 1 b in terms of dimensions and positioningon the inlet pipe ZR in a device, can be electrically or inductivelyheated.

For the electrical variant, heating wires, coils and other elements arepreferably disposed in the wall of the immersion pipe isolated from theproduct and environment. For the inductive variant, at least majorportions of the immersion pipe are preferably made from ferromagneticmaterial. Since a voltage source is necessary for electrically heatingthe immersion pipe and an appropriately strong magnetic source is neededfor inductive heating, both variants are used under specific conditionsonly.

LIST OF REFERENCES

-   A Outlet orifice-   AA Outlet connector-   AL Outlet pipe-   AM Coolant outlet-   B Freeze-thaw container-   BB Base-   BD Lid-   BW Wall-   E_(Ho) Top horizontal portions-   E_(Hu) Bottom horizontal portions-   E_(V) Vertical portions-   E_(Z) Central portion-   F_(MAX) Maximum filling level of the container-   I Interior-   KS Cooling coil-   KL Cooling pipe-   L Container longitudinal axis-   P Base stand-   T Deepest point of the container-   ZM Coolant inlet-   ZO Orifice-   ZR Inlet pipe-   ZS Inclined portion of the ZR-   ZV Vertical inlet pipe piece-   1, 1′, 1″ Device-   10, 10′, 10″ Freeze-thaw container-   11 Container interior-   12 Insulation-   20 Lid of B-   30, 30′ Base of B-   31′ Bottom outlet orifice-   40, 40′ Wall of B-   50 Cooling element-   51 Vertical part-piece-   52 Radial part-piece-   53 Stopper-   54 Inlet, inlet port-   55 Outlet, outlet port-   56 Top horizontal part-piece of the cooling coil-   57 Bottom inclined radial piece 60, 60′ Immersion element, immersion    pipe-   61 Top vertical part-piece-   62 Top horizontal part-piece-   63 Vertical part-piece-   64 Fitting-   65 Inlet connector-   66 Outlet connector-   67, 68, 69 Valves-   70 Return line-   71 Inlet connector-   72 Valve-   73 Valve piece-   74 Tubular leg-   75 Outlet orifices-   80 Immersion pipe-   81 Bottom orifice-   82 Connector (immersion pipe)-   90 Spray pipe-   91 Spray pipe connector

1. Device for freezing, transporting and thawing fluids, in particularsterile fluids, solutions and suspensions for the chemical,biotechnological, pharmaceutical and food industry, with a container(10, 10′) comprising a lid (20, 20′, 20″), a wall (40, 40′) and a base(30, 30′), and at least one heat exchanger element (50, 50′) activelycommunicating with the fluids with which the container is filled so thatthey can be cooled or heated, characterised in that an immersion pipe(60, 80) is actively connected to at least one heat exchanger element(50, 50′, 30, 30′, 40, 40′) via at least a part-region of itslongitudinal extension and that a return line (70) is provided on thecontainer (10, 10′) in a region above the maximum filling level(F_(MAX)), preferably in the lid (20, 20′), so that a fluid liquefiedduring a thawing operation and fed off via the immersion pipe (60, 80)from the deepest point of the container (10, 10′) and pre-heated can bepumped via the return line (70) onto still frozen fluid from above. 2.Device as claimed in claim 1, characterised in that the immersion pipe(60, 60′, 80) establishes a connection communicating between a firstbottom orifice (63′, 81) in the region of a deepest point in theinterior of the container (10, 10′) and a top-end second orifice (66,82) disposed at the container (10, 10′) or at the lid (20, 20′, 20″). 3.Device as claimed in claim 1, characterised in that the immersion pipe(60, 60′, 80) is in an active thermal connection with the heat exchangerelement (50, 50′, 30, 30′, 40, 40′) by means of a part-piece (63, 63′)from more or less the deepest point of the container up to a maximumfilling level (F_(MAX)).
 4. Device as claimed in claim 1, characterisedin that the heat exchanger element comprises a cooling coil (50, 50′)and the immersion pipe (60, 60′) is run coaxially in a part-piece (51,51′) of the cooling coil (50, 50′) along a part-region of itslongitudinal extension and is actively in thermal, preferably direct,contact with it.
 5. Device as claimed in claim 4, characterised in thata vertical part-piece (63) of the immersion pipe (60) is run coaxiallyin a central portion (51) of the cooling coil (50) and along alongitudinal axis (L) in a region which extends more or less from themaximum filling level (F_(MAX)) to the deepest point of the container(10).
 6. Device as claimed in claim 5, characterised in that the axialpart-piece (63) of the immersion pipe (60) forms an internal wall of thehollow cylindrical, central portion (51) of the cooling coil (50) sothat the immersion pipe (60) and cooling coil (50) are integrallyconnected to one another as a “pipe in pipe” arrangement in this region.7. Device as claimed in claim 1, characterised in that the heatexchanger element comprises a double-skin base (30, 30′) and adouble-skin wall (40, 40′), and the immersion pipe (60, 60′) is runinside or outside the base (30, 30′) and wall (40, 40′) across apart-region of its longitudinal extension and is in active thermalcontact with them, preferably in direct contact.
 8. Device as claimed inclaim 1, characterised in that the return line (70) extends through thelid (20, 20′) and opens into at least one, preferably two dischargeorifices (76, 77) above the maximum filling level (F_(MAX)) which aredisposed so that the pumped fluid is directed onto top part-pieces ofheat exchanger elements (50, 50′, 40, 40′), preferably of the coolingcoil (50, 50′), and reduce the formation of foam.
 9. (canceled) 10.Method of thawing frozen fluids, in particular sterile fluids, solutionsand suspensions for the chemical, biotechnological, pharmaceutical andfood industries in a device (1, 1′, 1″) as claimed in claim 1,characterised in that a warm medium is fed through at least one heatexchanger element (50, 50′, 30, 30′, 40, 40′) and frozen fluid in animmersion pipe (60, 80) actively connected to the at least one heatexchanger element (50, 50′, 30, 30′, 40, 40′) is thawed, after whichthawed fluid can be drawn off from the deepest point in the interior ofa container (10, 10′) through the immersion pipe and pre-heated beforeit is pumped via a return line (70) onto the fluid still contained inthe container from above.